Mitchell Waters
Media Studies
How does a Web Site Work – Task 2
Types of Images and Animation
JPG is the most used image file format. Digital cameras and
web pages normally use JPG files - because JPG heroically
compresses the data to be very much smaller in the file.
However JPG uses lossy compression to accomplish this
feat, which is a strong downside. A smaller file, yes, there is
nothing like JPG for small, but this is at the cost of image
quality.
GIF was designed by CompuServe in the early days of computer 8-bit video, before
JPG, for video display at dial up modem speeds. GIF offers transparency and
animation. PNG and TIF files can also optionally handle the same indexed color
mode that GIF uses, but they are more versatile with other choices too (can be RGB
or 16 bits). But GIF is still very good for web graphics (i.e., with a limited number of
colors). This is both an image type and animation.
PNG can replace GIF today (web browsers show both), and
PNG also offers many options of TIF too (indexed or RGB, 1
to 48-bits, etc.). PNG was invented more recently than the
others, designed to bypass possible LZW compression
patent issues with GIF, and since it was more modern, it
offers other options too (RGB color modes, 16 bits, etc.).
One additional feature of PNG is transparency for 24 bit RGB
images. Normally PNG files are a little smaller than LZW
compression in TIF or GIF (all of these use lossless compression, of different types),
but PNG is slower to read or write. That patent situation has gone away now, but
PNG remains excellent lossless compression. This is both an image type and
animation.
SWF is a file extension for a Shockwave Flash file format created by Macromedia
and now owned by Adobe. SWF stands for Small Web Format. SWF files can
contain video and vector based animations and sound and are designed for efficient
delivery over the web. This is both an image type and animation.
Types of Videos
(AVI) Audio Video Interleaved (also Audio Video Interleave), known by its initials
AVI, is a multimedia container format introduced by Microsoft in November 1992 as
part of its Video for Windows software. AVI files can contain both audio and video
data in a file container that allows synchronous audio-with-video playback. Like the
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Media Studies
DVD video format, AVI files support multiple streaming audio and video, although
these features are seldom used. Most AVI files also use the file format extensions
developed by the Matrox OpenDML group in February 1996. These files are
supported by Microsoft, and are unofficially called "AVI 2.0".
MPEG-1 is a standard for lossy compression of video and audio. It
is designed to compress VHS-quality raw digital video and CD
audio down to 1.5 Mbit/s (26:1 and 6:1 compression ratios
respectively) without excessive quality loss, making video CDs,
digital cable/satellite TV and digital audio broadcasting (DAB)
possible.
Today, MPEG-1 has become the most widely compatible lossy
audio/video format in the world, and is used in a large number of
products and technologies. Perhaps the best-known part of the
MPEG-1 standard is the MP3 audio format it introduced.
QuickTime File Format (QTFF) is a computer file format used natively by the
QuickTime framework
Because both the QuickTime and MP4 container formats can use the same MPEG-4
formats, they are mostly interchangeable in a QuickTime-only environment. MP4,
being an international standard, has more support. This is especially true on
hardware devices, such as the Sony PSP and various DVD players; on the software
side, most DirectShow and Video for Windows codec pack include an MP4 parser,
but not one for QTFF.
Windows Media Video (WMV) is a file type which can contain video in one of
several video compression formats developed by Microsoft. The original video
compression format used in the file, also known as WMV, was originally designed for
Internet streaming applications, as a competitor to RealVideo. The other
compression formats, such as WMV Screen and WMV Image, cater for specialized
content. After standardization by the Society of Motion Picture and Television
Engineers (SMPTE), WMV 9 adopted for physical-delivery formats such as HD DVD
and Blu-ray Disc.
RealVideo is a suite of proprietary video compression formats developed by
RealNetworks – the specific format changes with the version. It was first released in
1997 and as of 2008 is at version 10. RealVideo is supported on many platforms,
including Windows, Mac, Linux, Solaris, and several mobile phones.
RealVideo is usually paired with RealAudio and packaged in a RealMedia (.rm)
container. RealMedia is suitable for use as a streaming media format that is one
which is viewed while it is being sent over the network. Streaming video can be used
to watch live television, since it does not require downloading the entire video in
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Media Studies
advance. Compression and decompression software for each version are called
"codecs".
Flash Video is a container file format used to deliver video over the Internet using
Adobe Flash Player version 6 and newer. Flash Video content may also be
embedded within SWF files. There are two different video file formats known as
Flash Video: FLV and F4V. The audio and video data within FLV files are encoded in
the same manner as they are within SWF files. The F4V file format is based on the
ISO base media file format and is starting with Flash Player 9 update 3. Both formats
are supported in Adobe Flash Player and developed by Adobe Systems. FLV was
originally developed by Macromedia.
Types of Audio
MIDI Files ("SMF" or *.mid files) are a popular source of music on the web, and for
musicians performing in clubs who need a little extra accompaniment. The files
contain all the MIDI instructions for notes, volumes, sounds, and even effects. The
files are loaded into some form of ‘player' (software or hardware), and the final sound
is then produced by a sound-engine that is connected to or that forms part of the
player.
RealAudio is a proprietary audio format developed by RealNetworks and first
released in April 1995. It uses a variety of audio codecs, ranging from low-bitrate
formats that can be used over dialup modems, to high-fidelity formats for music. It
can also be used as a streaming audio format that is played at the same time as it is
downloaded. In the past, many internet radio stations used RealAudio to stream their
programming over the internet in real time. In recent years, however, the format has
become less common and has given way to more popular audio formats. RealAudio
was heavily used by the BBC websites until 2009, though it was discontinued due to
its declining use. BBC World Service, the last of the BBC websites to use RealAudio,
discontinued its usage in March 2011
Windows Media Audio (WMA) is an audio data compression technology developed
by Microsoft. The name can be used to refer to its audio file format or its audio
codecs. It is a proprietary technology that forms part of the Windows Media
framework. WMA consists of four distinct codecs. The original WMA codec, known
simply as WMA, was conceived as a competitor to the popular MP3 and RealAudio
codecs. WMA Pro, a newer and more advanced codec, supports multichannel and
high resolution audio. A lossless codec, WMA Lossless, compresses audio data
without loss of audio fidelity (the regular WMA format is lossy). WMA Voice, targeted
at voice content, applies compression using a range of low bit rates.
Mitchell Waters
Media Studies
MP3 is an audio coding format for digital audio which uses a form of lossy data
compression. It is a common audio format for consumer audio streaming or storage,
as well as a de facto standard of digital audio compression for the transfer and
playback of music on most digital audio players.
The use of lossy compression is designed to greatly reduce the amount of data
required to represent the audio recording and still sound like a faithful reproduction of
the original uncompressed audio for most listeners. An MP3 file that is created using
the setting of 128 kbit/s will result in a file that is about 1/11 the size of the CD file
created from the original audio source. An MP3 file can also be constructed at higher
or lower bit rates, with higher or lower resulting quality.